Control system



R. D. JUNKINS CONTROL SYSTEM July 29, 1943.

Filed Jafl. 5, 1940 e Sheets-Sheet s 3nventor mug n M, WW

muNiOzoow July 20,-1943. R. D.- mums ,5

CONTROL SYS'iEM "Filed Jan. 5 1940' e Shefs-Sheet 4 FEED -n n u u 78. I, FIG. 5

. I 7. v I

3nventor R. D. JUNKINS July 20, 1943.

CONTROL SY STEM Filed Jan. 5, 1940 6 Sheets-Sheet 5 Enven'tor 29.5mm 20 wmw 20o mh 2076mm y 1 R. D. JuNKiNs CONTROL. SYSTEM 6 Sheets-Sheet 6 FiledJan. 5, 1940 "FIG. 7

lnnen tor FROM TEMPERATURE Patented July 20, 19 3 UNITED Raymond D, Junkins, Cleveland Heights, Ohio 2,324,512 CONTROL SYSTEM Application January 5, 1940, Serial No. 312,516

2s Claims. (01.196-132) This invention relatesto methods of and apparatus for fluid processing or treating systems, particularlyof the forced circulation type wherein the fluid to'be processed or treated is supplied I to the inlet of a heated path under pressure and discharges at the other end of the path-either as a liquid, a vapor,-or a liquid-vapor mixture. Such systems contemplate the generation of steam from water, the processing of petroleum'hydrocarbons; or any analogous fluid treating .or processing.

While} have chosen to illustrate and describe as a preferred embodiment of my invention the generation of steam in a forced flow vapor generator, it is to be understood that this is'by way of liquid from the separator is preferably through 1 example only and that the invention is equally applicable to the processing of petroleum hy.-' drocarbons, or in fact of any fluid in forced circulation through a heated path.

The particular vapor generators here under consideration are of the forced flow type having a fluid flow path including one or more long smallsection, which acts'as a separator to divide liquid and vapor. The vapor is then passed through a superheater, while the excess liquid carried through the tubes of the generating section for the purpose of wetness andpreventing scale de: posit, isdiverted out of the separator under regulated conditions and is either recirculated to the entrance of the flow path or returned to the hot well'or sent to waste. It is'usual that a portion of the liquid collected in the separator is sent to waste to keep the concentration below a predetermined value." The diversion or spillover of two'pat'hs, either or both of which may be under automatic control comprising a variable or adjustable spillover.

The excess of liquid over vapor generated and which may be completely or partially recirculated,

bore tubes, in which the fiow m the path is mmated by the entrance of liquid under pressure at one endand the exitof vapor only at the other end and characterized by an inflow of liquid normally greater than the outflow of vapor, the difierence being diverted from the path intermediate the ends thereoi.

Such a vapor generator, having small liquid storage, and operated with wide rangecombustion devices, forms a combination rendering practical extremely high heat release rates with the consequent ability to economically handlepractically instantaneous load changes from minimum to maximum, and vice versa, without heavy standby expense, and is particularly suitable for operating conditions such as locomotive or marine may comprise twenty, thirty, or even fifty percent of'the liquid entering the flow path under pressure. The same is true in the case of a processing of petroleumhydro'carbons, in which in fact the percentage by weight of liquid leaving the heated path may be as much or greater than the weight rate of vapor flow.

The separator forms in effect a bulge in the I forced circulation path,and is a relatively quiesservice w'hereloadvariations are of a'wide range and are required to be met substantiallyinstantaneously.

The generator has a minimum liquid storage capacity with a maximum heat absorbing surface cent zone'to which the excess liquid, as well as the vapor, is discharged. In the case of a vapor generator the excess liquid carries the solids from the generating portion of the path to the sepav rator. A portion of the spillover from the sepa-' ratormay be sent to waste or to the hot well or to other apparatus such as a heat exchange. An'

other portion of the spillover may be recirculated andintroduced at the entrance of the generatingsurface or at the economizerheader. Itis particularly in the control of such recirculated liquid 'that'I am concerned in the present invention.

Through the utilization of the present invention I am enabled'to recirculate a considerable percentage or the liquid entering the flow path and withladvantageous ,;results. For example,

so disposed and arranged, as to-be substantially instantaneously responsive to rapid changes and wide diversities in heat release rate in the furnace.

The eat absorbing surface, or flow path'rorthe wor fig medium,

is preferably comprised of a plurality of long small-bore tubes with" an enlarlementmrererably at the end of the generating such recirculationmay comprise twenty, thirty,

or even fifty .per'centbf the liquid entering the flbwlpath under pressure Solong assuch recirculation may be accomplished withoutfloss or heat and without the expenditure of considerable power there are gained thereby. I

material advantages to be In a forced circulation type of vapor generator comprising a once through fluid path of one or more long small-bore tubes with a very small liquid storage and a very high rate of evaporation, it is known that the vaporization zone within the path is the location where substantially all of the solids carried by the liquid will be deposited or left in suspension through vaporization ofliquid. agitation of the liquid, they will serve'to continuously increase the concentration of solids in the liquid remaining in the tube path in and ahead'of the vaporization zone. In the separator type of forced circulation boiler with a material excess of liquid inflow to the path over vapor outflow from the path, the econoniizer and generating section prior to the separator will be at all times wetted to prevent scale formation and will be provided with suflicient liquid to. wash all of the solids into the separator. Thus'the separator comprises a relatively quiescent zone where separation of vapor and liquid may occur and to v which substantially all of the solids of the liquid inflow are carried.

It has been known to continuously divert excess liquid from the flow path at the separator and to discharge such liquid to waste. This means a considerable constant loss of liquid and of the heat contained therein, and the tendency is to reduce the excess liquid to as low a value as possible to save ,this loss Preferable operation would be to have a materially greater excess of liquid flowing through the economizer and generating sections than is economically possible ii all of the excess is to be discharged to waste from the separator drum.

Such a vapor generator has substantially no heat storage capacity either in the metal parts or in the small volume of liquid stored. It is capable however of very fast changes in'heat release and absorption rate. However, through the advantage of my invention, I have been able to If not deposited, due to the extreme materially increase the speed atwhich load changes may be made through the utilization of the liquid stored in the separator-drum at substantially vaporization temperature. Furthermore, I accomplish a recirculation of a very large percentage of the liquid inflow at substantially vaporizing temperatureand without an increase in feed pump capacity or power. requirements, and in fact under certain conditions of design I heat potential. With a larger percentage of inflow being recirculated instead of to drain. the main feed pump need handle less liquid and require less power.

In the multi-circuit path of a forced flow vapor generator it is usual to-introduce flow restrictors or equalizers between the economizer and vapor generating sections of the path, to attempt to attain equalization of flow, heating, and other variables through the parallel paths of the generating section, and to prevent overheating of one tube as compared to another. Flow restrictors are usually sections of tubing of relatively small diameter introducing a resistance to flow of several times that of the tube path following, so that variations in flow resistance 01' said following tube path will be of minimized effect relative to the total resistance including the flow restrictors. Through multiplying the flow resistance several times in this manner it is, of course. necessary to overcome such resistance with feed pump power.

I propose to replace such flow restrictors ,by injectors inserted in the several tube portions of the path at the entrance to the vapor generating section, utilizing the pressure drop therethrough to .pump or recirculate the liquid from the separator drum, automatically regulate .the supply of liquid to the individual paths, and with the knowledge that such a. plurality of injectors will tend to be self-equalizing insofar as heat and flow distribution between the different tube paths is concerned. Any generating tube which has a tendency, due to unequal application of heat for example, to'generate more steam than its parallel tubes, tends to become overheated through the presence of generated steam within the tubes rather than a. wetting liquid. While the previous flow restrictors Jor balancing resistors tend to minimize the effect of inequalities in tube resistance, and thereby to equalize flow in the parallel tube circuits, the substitution of.

an injector for each flow restrictor, with a nozzle resistance commensurate with that of a restrict'or, serves not only to retain the advantage oi flow equalization but additionally tends toward an equalization of heat, temperature, density, and other properties of the vapor-liquid mixture leaving the tubes.

have been able to materially reduce the feed pump size or power requirement.

In addition, the invention accomplishes the very necessary desideratum of balancing the plurality of parallel circuits insofar -as resistance, flow, temperature and heat are concerned.

7 Through the recirculation of a very large perlated liquid into the flow path entrance through the agency of injectors with approximately the same pressure drops as the previously used balancing flow resistors, to serve as circulating pmnps to increase the rate of circulation in the vaporization zone without requiring the pumping of extra water by the main feed pump nor the loss of high potential heat occasioned bydneans of the spillover which formerly must go to the feed water heaters or some similar point of low By way of example; should any particular circuit tend to become overheated due either to decrease in flow or increase in heat input (as by particular circuit is reduced and likewise the tendency toward excessively high ratio oi steam to water, or high-dry steam temperatures leaving the circuit is checked. Similarly, it a particular circuit receives insuiilcient heat, a smaller proportion of that circuit will be Occupied by steamandthecircuitreduoed. 'l'hk results in a decrease in injector delivery plusureandthusanincreaseintheamoimtotrecirculated water pmnpedbytheimector undentering that circuit. The water withdrawn trcm theseparator drum for recirculating throughtbe temperature of the recirculated water.

generating portion oi the flow path is preferably introduced at the entrance to the generating portion where the temperature of the water coming from the economizer is materially lower than the Thus since the net temperature of the water entering the generating portion of the path depends on the ratio of recirculated water to feed water, it is irgaeased and the rate of steaming is acceler- & r

Thus the use of injectors in place of balancing resistors tends to automatically balance the tubes in the parallel circuits insofar as flow, heat, temperature, etc. are concerned.

No such heat and/or temperature equalizing tendency is obtained with flow restrictors. When they alone are used, one must depend upon the total resistance, that is, resistors plus tube re- ,sistance must be near enough alike in the different circuits to tend to equalize flow therethrough.

Through my invention, by the substitution of injectors for-flow resistors, there is a greater tendency toward circuit equalization offiow, heat, and temperature, since I have not lost the action of-high pressure drop in equalization of flows and at the same time I have gained a tendency toward equalization of fluid thermal conditions leaving the circuits by automatically regulating the feed temperature entering the circuits in an opposite sense to the amount of steam being generated in any particular circuit.

The scheme consists essentially of elimination of the present balancing resistors or flow equalizers and the substitution therefor of injectors with approximately the same pressure drop which will serve as circulating pumps for the individual tube circuits to increase the rate of circulation pumping of extra water by the main feed pump. The pressure drop of the present balancing resistors may be used as energy through the injector action to pump at leasttwenty to thirty.

percent of the flow rate back from theseparator drum to the entrance of the vaporizing sec-v tion.

- It does not appear necessary to go into the reasons for employing a plurality of long 'smallin the vaporizing zone without requiring the e bore-tubes for theforced circulation flow path,

inasmuch asthe. advantage is well recognized in the art. Suflice it to say that having such construction it is of prime importance that the plurality of circuits be equalized insofar as flow,

heat, temperature, density, etc. are concerned...

The particular features of my present invention to be described and claimed herein relate to the supplying at the entrance of a forced circula-' tio'n flow path fluid containing liquid in excess of that which willbe vaporized during its treatment in the path. In withdrawing near the exit of the treatment zone a flow of liquid, gas, vapor, or a mixture of them, and recirculating it to the entrance at to an early location in .the flow path. Thus the fluid passing under pressure through the. treatment zone is preferably in-part made up of recirculated fluid. It' is in the control of the recirculated fluid that my present in- I vention is particularly adapted.

While it is true that 1 am principally describing my invention in connection with a forced circulaton vapor generator, it must beremembered I a that other treating and processing systems, such fluid flow passages 6; I; 8, 9 and lo constituting temperature, density, etc.'is of prime importance. It is not necessary that the forced circulation path either for a vapor generator or for a petro-i leum processing system comprise a'plurality ofv parallel circuits, but may in fact be a single tube bear Fig. 6 diagrammatically illustrates an embodi- 'ment of my invention particularly adapted to petroleum hydrocarbon treatment. 7 Fig. 7 illustrates the invention applied to a forced circulation fluid path, such as illustrated in Fig. .3.

Fig. 8 is a modification of Fig; 'I.

The drumless forced flow vapor generator to which the present invention is particularly directed is diagrammatically illustrated in Fig. 1

to indicate gas flow, working fluid flow, and heat absorbing surface, arranged as contained within the enclosure represented by the dot and dash lines.

,The flow path for the working medium is coinprised of longsmall-bore tubes brought together at suitable headers. Th generator includes an 'economizer I at the cooler end of the gas passage and which receives liquid from a pump which maybe connected to a hot well. The

' pump may be of any suitable type or characteristic adapted for the service.

The liquid from the economizer outlet header 2 is conveyed by a tube 3 to amanifold 4 from i which the liquid is distributed to the generating section through, in this 'instance,-five injectorsi,

each of which has a certain resistance drop preferably greater than the particular fluid flow passage which it serves, and whereby the liquid is proportionately distributed to each of the tubular the generating section of the assembly which comprises floor, wall, screen and roof portions as indicated.

for example as the processing of a petroleum hydrocarbon, also employ a pluralityof long small-' bore tubes for the forced flow path, and here again the necessity of equalization of flow, heat.

These .flve flow circuits comprising the vapor generating surface tangentially enter a bulge in the fluid flow path which is in the form of a separating chamber H for dividing the fluid into liquid and vapor, the vapor passing to a superheater l2 and the excess liquid being diverted from the fluid flow path-through a pipe I: to recirculation by means of the injectors or to waste or the hot well.

Through the utilization of injectors-between the economizer and generating portions of the path I have made use of the otherwise wasteful pressure loss of the previously known flow equalizers or restrlctors. In other words. the injectors of. the plurality of circuits would have substantially the same pressure drop as the previously.

mentioned flow equalizers, but would utilize such pressure drops in actually pumping into the generating section the recirculated spillover from the separator There is thus no extra pump required for the recirculated liquid. There a is substantially no loss in heat in the large volume of recirculated spillover. This recirculated liquid at nearly vaporizing temperature is available at the inlet to the generating section at all times, and as previously brought out is fed proportionate to the rate of operation of the generator as a whole. In other words, as demand upon the generator increases, the injector action will automatically increase, thus drawing a greater volume of recirculated spillover from the separator drum, utilizing the stored liquid thereof, and at no additionalv pumping expense. ,The additional volume of highly heated liquid entering the generating section will materially speed up the loadtaking-on ability of the generator as a whole. This is further amplified due to the swell of the liquid within the separator when load suddenly increases and pressure on the separator correspondingly suddenly decreases. Such swell or increased volume of liquid within the separator will afiord a very welcome additional supply of highly heated liquid to the entrance of the generating section. l

Additionally, as previously mentioned, the use of the injectors serves a primary and highlyimportant function in heat and flow equalization between the plurality of circuits as compared to the fixed flow equalizers of prior constructions. Equalization between the various circuits of the generating section will -be automatic at times of change in load and self-equalizing to counteract the adverse efiects of localized heating or other sources of trouble in operation. Such equalizations will be of flow, temperature, heat, density, etc.

The heat source" of Fig. 1 is illustrated as having an oil burner I4 supplied by a pipe [5, and controlled by a regulating valve [6. The heat source may comprise any well known fuel burning arrangement and have the ordinary provisions for initial ignition, safety features, etc.

In Fig. 1 the spillover pipe I3 has a control valve'll leading to waste or to the hot well. Branching from the pipe I3 to the recirculating injectors is'a pipe l8 having a regulating valve l9, by-passed by a fixed rate of flow by-pass 20.

In Fig. 2 I illustrate diagrammatically the flow path of the working medium without respect to the sequence of heating. The various tubes or parallel circuits of the vapor generating section are brought together and passed as a whole through apressure differential responsive device prior to entering the separator drum. Certaininstruments and regulating valves in connection with the system are shown in Fig. 2 and will be referred to hereinafter in connection with the other figures of'the drawings.

It will'be understood that any well known form of injector may be utilizedin the individual flow circuits and that the particular injector forms no part of the present invention, but will'be designed to give desired pressure drop, flow capacity, and characteristics.

It will be f urther understood that while the vapor generating surface of Fig. 1 is shown as comprising five parallel flow paths, and that of Fig. 2 as comprising two parallel flow paths, these the speed of the pump 22, but is further influare representative only, and the flow paths may 2,324,513 which I have therefore illustrated inFig. 3 merely diagrammatically. From the economizer section the fluid passes to andthrough thegenerating section, discharging into the separator II. From the separator, vapor passes to and through the superheater 12 to a main turbine 23 illustrative of a vapor consuming device. Products or combustion pass successively through the generating section, superheater, and economizer and may to be driven by the same shaft and at the same I speed, it will be understood that the "necessary gear reduction or driving connections between the several devices are known and would be properly designed as to relative speed, power, etc., and that I merely intend to indicate that the auxiliary turbine 24 drives the devices 22, 25 and 26 simultaneously and in unison.

The rate of supply of fuel oil to the burner l4 through the pipe I5 is primarily controlled by the speed of the oil pump 26, but the supply of oil is further regulated by the throttling of the regulating valve l6.

The rate of supply of air to support combustion is primarily determined by the speed of the blower 25, but is further under the control of a damper 21 positioned at the-inlet to the air blower 25.

The rate of supply of liquid under pressure through the conduit 2| is primarily controlled by' enced through the positioning of a regulating valve 28 at the suction side of the pump.

29 represents means responsive to liquid level within the separator II and constitutes a pressure casing enclosing a mercury U-tube connected across thevertical elevation of the separator. A float is adapted to rise and fall with the surface of the mercury in one leg, and to thus cause a positioning of a pointer 30 relative to an index 3| to advise the instantaneous value of liquid level and to further vertically position the stem 32 of a pilot valve 33 to establish one or more air loading pressures representative of liquid level. Such an air loading pressure decreasing with rise in level is transmitted through the pipe 34 to the averagingrelay 35. Air loading pres sure increasing with rise in level is transmitted through the pipe 36 to a diaphragm actuated valve I I.

A rate of flow meter 38 continuously indicates the weight rate of vapor outflow through the conduit 39 and positions a. pilot stem 40 in accordance therewith, The air loading pressure repretions in'liquid level within the separator H. For a example, liquid inflow is held roughly in proportion to vapor outflow and is. readjusted to maintain desirable level within the separator. While the rate of liquid inflow is;not entirely under the control of regulating valve 28, it is primarily so, for the pressure drop across the valve 28 is utilized in positioning an auxiliary turbine governor 42,

A Bourdon tube 43 is sensitive to vapor outflow pressure and positions a pilot valve 44 to estabposed upon lish anair loading pressure representative of vapor outflow pressure effective in positioning the damper 21 for readjusting the supplyof air for combustion. I

The pipe |3 leads from the separator II to the regulating valve II which latter is under the control of the level responsive device 29. Should level within the separator reach a predetermined high level, the level responsive device 29 will so positionthe pilot stem 32 ,that an air. loadin pressure will be established through the pipe 36 upon the valve l1 and cause the valve to open quickly and in large degree to take care of such emergency conditions until the level is again brought down to below the emergency point.

As previously mentioned, the pipe l8 branches from the pipe l3 and leads to the injector or injectors 5at the entrance to the generating sec- I tion. The pipe It has a fixed resistance in one branch and a regulating valve IS in the other branch, As shown, the regulating valve I!) may be positioned in accordance with the load- .ing pressure established by the weight rate of flow meter 38 through the air loading pipe leading from the pilot valve 40. -The air loading pressure established by the pilot 4D is normally effective upon the differential relay 35' in value and therefore quite independent perature, pressure, location, etc.

A particular feature of the present invention is a control of the heating and/ or of recirculation responsive to a determination of the density of the liquid-vapor mixture leaving the generate section and passing to the separator In Fig. 3 I have shown a conduit leading from th generating section to the separator II. In the conduit 50 I have located an orifice or similar restriction 5| which may be a'Venturi tube,

flow nozzle, or any suitable and well known device for creating a pressure differential representative of the volume rate of flow of fluid therethrougli.

Connected to the conduit 50 at Opposite sides of the orifice 5 I, by means of the connecting pipes 52, 53, is a diflerential pressure responsive device 54 comprising a mercury U-tube on the surface of one. leg ofwhich is a fioat positioned responsive to and representative of the differential in pressure existing across. the orifice 5| The float is adapted to position an indicator arm 55 relative to an index 56, and at the same time to position conjunction with a loading pressure responsive to separator drum level, jointly, to. position the valve 28. By openingvalvelfi and closing valve $1 I may make the loading pressure which is representative of weight rate of vapor outflow' effective in positioning the regulating valve l9 so that the liquid recirculated to the entrance of thegenerating section from the separator II will vary in accordance with loadas represented by the weightrate measure of vapor outflow. This recirculation varying with load is superima constant recirculation passing fixed resistor 20. r

at' it an a r pressure pipe leading from a pilot valve 59. The air loading pressure through the I indicate established the pilot 89' is representative or density of the l quid, vapor, or liquid-vapor mixture entering the separator I I from the generating section of the flow path." Normally the rate ofsupply of fuel through the valve Hi -to the burner it is regulated in accordance withsuch densitv measurement. However by closing the valve M and opening the valve 4'! I may additionally place the recirculatlon'valve I9 under the control of the pilot valve 49, or-in accordance with density of the fluid entering th -separator ii. Thus, I may if desired'control either the heating of the path. or the recirculation of working medium, or both, in accordance withdensity of the fluid entering the separator. Various combinations of such control may readily be obtained by installing the proper valves in the air loading lines 45, 48. I will now describe, with reference to Fig. 3, the arrangement for obtaining an air loading pressure representative of density of the fluid entering the separator I I. I

I desire it to be understood that in speaking of density in this description and in the claims I use the term in its well understood and generic definition and meaning, such as has been established by the International Critical Tables, Bu-

reau of Standards, and other authorities as fol-' lows: r 1

Density of any substance (a. liquid, gas, liquidgas mixture, or a solid) is expressed in units of weight per unit of volume, as for example, pounds per cubic foot. It is an absolute or concrete tact relative to a resistance62.

a contactarmalong a resistance 51 so that the resistance 51 will be directly representative of I have also indicated in Fig. 3 a thermocouple T1 for determining the temperature of the fluid passing through the conduit 2|, a thermocouple T2 sensitive to temperature ofthe mixture in the (conduit 50, and a thermocouple'Ta sensitive to temperature of the steam leaving the superheater i2.

As clearly illustrated in Fig. 3, the differential pressure meters 54, 53 are inter'connectedin a Wheatst one bridge to determine the value of density of the mixture passing through the conduit 50 to the separator H. I have previously indicated that the resistance values 51', 82 are continuously' representative of differential pressure across the orifices 5|, 59 respectively.

The relation between volume flow rate and differential pressure is:

Q=cMV2gh (1) Where Q cubic feet per second f c coefllcient of discharge M= =meter constant (depends upon pipe diameter and diameter of orifice hole) g acceleration of gravity =32.l7 ft. per sec.- per sec.

h =difierential head in feet of the flowing fluid The coeiiicient of discharge remains substantially constant for any one ratio of orifice diameter to pipe diameter, regardless of the density or specific volume of the fluid being measured.

With 0, M and VA: all remaining constant, then Q varies as the /h.- Thus it will be seen that the float. rise of the meters 54, 58 is independent of variation in density or specific volume of the fiuidyat the two points of measurement and that of temwill increase with decrease in density of the fluid, and vice versa.

This may readily be seen, for if it were desired to measure the flowing fluid in units of weight,

Formula 1 becomes:

W=cM /2ghd Where W=rate of flow in pounds per second d=density in lbs. per cu. ft. of the flowing fluid h=diflerential head in inches of astandard liquid such as water M=meter constant now including a correction to bring h of Equation 1 into terms h of Equation 2 Assuming the same weight rate of flow passing successively through two similar spaced orifices 59, 5|, and with a change in density of the flowing fluid as may be caused by the heating means, then the density at the second orifice 5| may be determined as follows:

Thus it will be observed, that knowing the density of the fluid passing the orifice 59 (in this case water), I may readily determine the density of the fluid passing the orifice 5| from the relation of differential pressures indicated by the meters 54, 58. Referring now to Fig. 3 it will be observed that the adjustable resistances 51, 52 comprise two arms of a Wheatstone bridge. A third arm includes a hand adjustable resistance 53, while a fourth arm includes a fixed resistance 54 and an adjustable balancing resistance 55. The adjustable resistance 55 (for balancing the bridge) is varied by movement of an arm 55, through the agency of a reversible synchronous motor 51, under the control of a galvanometer 58.

The motor 51 is of the self-starting synchronous type of alternating current motor and is shown as having normally deenergized opposed fields. unbalanced, then the needle of the galvanometer 58 will move either clockwise or counterc1ockwise, thereby energizing one of the flelds of the motor 51, resulting in a positioning of the arm 55 in direction and amount over the resistance 55 to balance the bridge and cause the galvanometer needle to return to neutral position. It

will be understood that the. necessary gear reduction is incorporated between the motor 51 and the arm 56, so that the arm 55 moves at a relatively slow speed.

The Wheatstone bridge thus serves to continuously determine the density of the fluid at the orifice 5| through solving Equation 3. Su h Should the Wheatstone bridge become density is continuously indicated on an index 59 by the movable arm 55.

Solving Equation 3.

Resistance 57och van-dit is expected that:

. R52 R51 It is known that bridge is:

R65: (R63 x115? and R65 represents d51- Thus the actual density of the fluid passing through the conduit 50 to the separator H is de- 5 terminedand indicated up the index 59. At. the same time the arm 55 positions the stem of the pilot valve 49, which may be of the type disclosed and claimed in the patent to Clarence pressure is established in the pipe 48 continuously representative of the value of density of the fluid in conduit 50.

It will be understood that each of the temperature responsive thermocouples T1, T2 and T3 is associated-with a known potentiometer device for positioning an indicator relative to an index to advise the value or the temperature, and at the same time to position the stem of a pilot valve, such as pilot 49, for establishing a fluid loading pressure representative of the particular temperature.

Under normal conditions of operation variations in vapor outflow effective upon the meter 38 will result in variations of auxiliary turbine in auxiliary turbine speed for changes inya'por' While in connection with Fig. 3 I have explained in detail the manner in which I determine the density of a liquid-vapor mixture, or in fact or any fluid, I do not believe that it is necessary to repeat such disclosure, either in the other figures of the drawings or in the description pertaining individually thereto. It will thus be understood that insofar as the remaining figures of the drawings are concerned the determination of density may be as explained in connection with Fig. 3. y

In Figs. 4 and 5 1 illustrate a treating .zone which may be applicable either to vapor generators or to the processing of petroleum hydrodrawings is that the recirculation-is accomplished by pumps and the distribution to the various the law of the Wheatstone Johnson 2,054.464 and wherein a fluid loading.

plurality of parallel circuits, and may include a parallel circuits is in accordance with some indication of rate of flow in the separate circuits.

Considering first the disclosure of Fig. 4, I have therein illustrated four parallel circuits (although the number is only representative) all feeding to a relatively quiescent separator zone H from which the conduit 39 leadsaway the vapor and/or gas, while the conduit I3 carries theliquid which has been separated out. Positioned relative 'to the outflow conduit 39 is a weight rate of flow meter 38 positioning apllot 40 to establish a loading pressure representative I 01' weight rate of flow of vapor and/or gas passing through the conduit 39. The loading pressure so established is used'in controlling a pump 10; as well as an averaging relay II in connection with each of the parallel circuits.

In each circuit, near theentrance thereof, I have located an orifice 'IZ-respohsive to differential pressure (representative of flow) in the particular circuit, and which differential pressure is effective in the averaging relay II. A loading pressure established by the averaging relay H is effective in positioning a control valve'l3 in connectlon with each of the circuits for'controlling the admission of liquid to the circuit from the pump 10.

Thus the arrangement is one wherein the liquid passed to the circuits by the pump I0, is (through the agency of the averaging relays ll) primarily in accordance with the total vapor outflow as measured by the device 38,- and secondarily readjusted in accordancewith the rate of flowof total flu d entering the heated path in a the particular circuit as measured by the orifice 12 of that circuit. Thus the total recirculated liquid is in accordance with vapor outflow measurement and is proportioned to the various circuits in accordance with the rate of flow or differential pressure relation between the cir-.

In Fig. I illustrate only two circuits in the treating zone, but this is representative of any desired plurality of circuits. Herein a rate oi flow meter H- is located in connection with one .of the circuits ancl'a rate of flow meter 15 in connection with the other of the circuits.-

Through differential linkage a pilot stem It is positioned to develop an air loading pressure in actual rate of flow in the two conduits to manthe cracking of oil.

previously described and utilized in similar fashion in connection with the additional apparatus and arrangement of Figs. 4 and 5. g s

In Fig. 6 I illustrate in diagrammatic fashion the application 01' my invention, to the processing of a petroleum hydrocarbon. as for example in Here again in general I illustrate a regulation and proportioning of the feed liquid to thevarious circuits in the conversion or vaporizing section of the fluid fiow path, and furthermore a regulation of the firing in accordance with variables in the operation of the unit. For example, in this drawing, the flow path is divided into a preheating section 19 and a conversion section 80 heated respectively by burners BI and 82.

A charge liquid enters through a conduit 83 to the preheating section 19 of the flow path which is heated by a burner or burners 8 l having fuel controlled thereto by means of a regulating valve 84. The fuel regulating valve 84 is controlled by a fluid pressure established by means of the pilot valve 85 positioned by the potentiometer device 86 sensitive to temperature T: of the flowing stream at the outlet of the preheating sec-' tion.

or damper 90. The conversion section leads its parallel circuits to a header from which a conduit 9! leads to a tower, reaction chamber, vapor separator, or other relatively quiescent zone 92 Q Where liquids, gases and vapors may separate.

In this particular arrangement the forced flow path is so arranged and proportioned that preferably no vaporization or liberation of gases or vapors occursin the preheating section 19; and all vaporization or liberation occurs within the conthe line H representative of relation between the tain the same in desired proportionality. This air loading pressure in the pipe 11 is used in positioning a proportioning valve I8 which. is fed by a-recirculating pump Illand serves to proportion the recirculated liquid to the two circuits of the treating path.

Thus while means are shown in Fig. 4 for readjusting by means of differential pressures, velocitles, or volume rate of flow in the various circuits, the apparatus of Fig. 5 utilizes weight rate of flow meters 14, 15 for proportioning the fluid to the circuits on a weight rate of flow basis.-' In Fig. 5 the pump 10 may be under the control of total load-as by a measurementof vapor out-- flow rate in a manner similar to that ililustrated in Fig. 4. a

It 'williurther be understood that the arrangement and apparatus as described in connection with the preceding figures, namely, that the plurality .of parallel circuits in the treating zone may be brought together prior to entrance into the separator, may be applied to the arrangements of Figs. 4 and 5. Furthermore, that the density of the total mixture prior to entering the entering the separator may be determined as version section 80. Thus it is normally expected that liquid only will enter the conduit 81 and that a liquid-vapor mixture will leave through the conduit 9| to the vapor separator 92.

The density of the liquid-vapor mixture in the conduit 9| is continuouslydetermined, or a manliestation thereof is determined, through the agency of the differential pressure meters 89,83,

:- and the Wheatstone bridge measuring system described in connection with Fig. 3. A density determini ng meter Dlll interrelates the resistances positioned by the differential pressure responsive devices 89, 93 to establish a fluid loading pressure effective for control of the fuel supply valve 9 of the conversion section 80.

In such a petroleum hydrocarbon processing system with a mixture of liquid, vapors and gases entering the relatively quiescent zone 92 through the conduit 9| there will be, besides the side cuts or drawofl's ofdesirable liquids, a discharge ofgases and vapors through the pipe 94 near the top of theseparator and a discharge of liquid through the conduit 95 near the bottomjof the separator.

. In the treatment of petroleum hydrocarbons I it is often desirable to compose, the charge liquid of charging stock with a certain amountof recirculation or recycle from some point in the process beyond the cracking unit or conversion section.

I have shown in Fig. 6 the possibility of introducing a recirculated fluid either to the entrance of the preheating section or to the entrance of the conversion section 80. In the latter event the recirculated fluid is. properly proportioned between the various parallel circuits of the conversion section.

I have illustrated the use of injectors as previously described, but additionally it may be necessar to provide pumps such as illustrated at 96 in the various fluid lines to insure a satisfactory pressure of the fluid for entering the conduit to which it is recirculated.

It will be observed that by an arrangement of selective valves I may introduce to the charge liquid of the conduit 83, selectively, either gases and vapors from the conduit 94, liquid from the conduit 95, or a mixture of liquid, gas and vapor from the conduit 9 I. At the same time, or as desired, I may introduce any of such fluids to the entrance of the conversion section 80 and properly-distribute the recycle fluid among the parallel circuits of this section. Additionally the control of recirculation or recycle fluid to either the preheating section or to the conversion section may be regulated in amount or rate of flow either on a volume or a weight rate basis responsive to density d91 of the mixture in the conduit 9| in accordance with the disclosure in connection with prior figures of the drawings. It will be understood that .the density of the fluid passing through the conduit 9| to the relatively quiescent separating zone 92 bears a relation to the total heat of said fluid so that theprocessing which occurs within the relatively quiescent zone 92 may be controlled by controlling the heat (through control of the density) of the fluid entering through the conduit 9|. Thus utilizing the density d91 as an indication of the heat of the fluid entering the chamber 92, I may regulate the heating of the preheating section and/or the conversion section, as well as the composition of the chargefluid entering either or both of these sections.

Fig. 7 is somewhat similar to Fig. -6, except that it relates more particularly to the forced circulation vapor generator of the type previously described in connection with Fig. 3. Herein I illustrate the possibility of recirculation of fluid either to the'entrance of the economizer section I or to the entrance of the generating section of the vapor generator. This, irrespective as to whether either or both ofv these sections is comprised of a single tube or of a plurality of 'parallel circuits. The fluid is introduced to the flow path by means of injectors in the present embodiment, and selectively may comprise spillover liquiu from the separator I I recirculated through the conduit 91, steam recirculated through the conduit 98, or a mixture of liquidand vapor as it enters the separator II and recirculated through the conduit 99. I illustrate in this drawing the control of further spillover from the drum H by a level indication of liquid within the drum so that there is no danger of the drum filling up and liquid entering the superheater.

The arrangement is further shown to have regulatingvalv'es I00, l0! and I02 placed in the con-' duits 91, 98 and.99 respectively, and positioned in accordance with loading pressures established from a density determination. Thus in Fig. '7, as in Fig. 6, a control of recirculation is had from density, and selectivity as to liquid, vapor, or a liquid-vapor mixture of fluid.

-It should be quite clear that theinvention is equally applicable to the vaporization of water, cracking or other treatment of petroleum hydrocarbons, or the processing of any fluid.

In the processing of petroleum hydrocarbons it will be appreciated that in starting up a cold unit, such for example as is illustrated in Fig. 6, there will be a certain period of time before stable or equilibrium conditions are attained. After' the system comes to a state of equilibrium wherein the density dill of the transfer line leading from the conversion section to .the relatively quiescent vapor separator or reaction chamber remains substantially constant, and with a relatively constant 'rate of flow of the charge to the unit, as well as stock characteristic, then the recycle or recirculation flow should be held constant and this can be accurately and satisfactorily controlled from transfer line density, such for example as determined by the device dn. It must be'kept in mind (referring particularly to Fig. 6) that while the preheating section 18 is shown as a single sinuous path it may well comprise a plurality of parallel circuits. In the same way the conversion section, which is shown in Fig. 5 as a plurality of parallel circuits, might even be a single sinuous tube.

I have previously mentioned that the density of the fluid mixture passing through the transfer line 9| to the reaction zone 92- is substantially a measure of the heat of the fluid passing therethrough, and thus is representative of a determination or indication of load upon the unit. The particular variables in the operation of such a unit 'with which I am concerned are those such as pressure, temperature, density, heat, rate of flow, load, etc., and this applies not only to the processing of hydrocarbon petroleums, but

also in the vaporization of steam, or in fact in the processing or treating of any fluid to which ,the present invention is adapted.

' While I have illustrated and described certain preferred embodiments of my invention I am not to be limited thereto except by the claims in view of prior art.

What I claim as new, and desire to secure by Letters Patent of the United States. is:

1. The method of operating a forced circulation fluid treating system wherein the entering fluid contains a'material percentage of liquid, which includes, heating the treating zone of the forced circulation path to a degree whereby a It is quite possible additionally to so arculating a portion of theunevaporated liquid from the separator to the entrance of the flow path, and varying the percentage recirculated responsive to a manifestation of density of the liquid-vapor mixture.

3. The method oioperating a vapor generator of the forcedflow type having a generating porder pressure-through a conflned'path comprising a preheatingand a conversion section, separately heating the sections of thepath, utilizing temperature determination of the fluid leaving the preheating section to regulate heating of that section, recirculating a portion of the treated fluid leavingthe conversion section to the ention, which includes, diverting a material percentage of the liquid from adjacent the vaporization zone of the path, reintroducing the diverted liquid to the generating portion, continuously passing a portion of the diverted liquid, and regulating the flow of the remainder responsive to density of the fluid adjacent the point of diversionof liquid from the path.

4. The method of operating a vapor generator of-the forced flow type having a separator between the generating and superheating portions of the flow path, which includes, recirculating a material percentage, of the liquid entering the generating portion, and varying the percentage recirculated responsive to' density of the liquid-Q .vapor mixture-of the fluid entering the separator. I l

5 The, method of operating a fluid treating system wherein a portion of the entering liquid previously treated fluid recirculated to trance thereof, andcontinuously utilizing conheating the sections of the path, passing the is'vaporized,'which includes, passing the liquid and vapor'mixture to a relatively quiescent sepa rator section, allowing the vapor to separate and pass away, recirculating a portion of the unvaporized fluid to the entrance of the treating zone, and varying the percentage recirculated re'sponsive to a manifestation of densityof the liquid-vapor mixture of the fluid.

6. The methodof processing petroleumhydrocarbon, which includes, flowing thefluid in a pressure stream through a path ofrelatively great length and smallidiameter, heating the path whereby a portion only ofthe entering liq-'- uid is vaporized, passing the resulting liquidvapor-gas mixture to a reaction chamber wherein, the liquid is separated, recirculating a'portion of the separated liquid to the entrance of the path,

, and continuously controlling the recirculationin I accordance with a continuous manifestation of fluid mixture entering the reaction 7 density of the chamber 7. The method of operating-a fluid treating system wherein a portion of the enteringliquid is vaporized, which'includes, passing the liquid and vapor mixture to a relatively quiescent separator section, recirculating a portion of the fluid to the entrance of the treating zone, and varying the percentage recirculated responsive to density of the liquid vapor mixture of the fluid.

. 8. The method of operating a fluid. treating 1 system wherein a portion of the entering fluid is vaporized, which includes, passing the liquid and vapor mixture to a relatively quiescent separator section, allowing the vapors to separate and pass drocarbon, which includes, flowing thefluid unliquid-vapor-gas mixture from the conversion section to a reaction chamber constituting a relatively quiescent separator zone, recirculating a portion of the vapors and gas leaving the reaction chamber separator zone to theinlet oi the path, and continuously regulating the amount 01' recirculation in accordance with a continuous determination of density of the fluid leavingthe conversion section.

, 12. The method of processing petroleum hyder pressure through a confined path comprising apreheating and a conversion section, separately heatingthe sections of the path, passing the liquidevapor-gas mixture from the conversion,

section to a reaction chamber constituting a relatively quiescent separator zone to effect a sepaa ration of the liquid, recirculating a portion of the I treated fluid to a selected location in the ,flow

-path, and continuously regulating- ,the recirculatlon rate in accordance with a continuous determination of density 01' the fluid leaving the conversion section. i

13. The method'of processing petroleum hy-' drocarbcn, which includes, flowing the fluid under pressure through a confined path comprising a preheating and a conversion section, separately heating the sections of the path, passing the liquid-vapor-gas mixture from the conversion section to a reaction chamber constituting a. relatively quiescent separator zone, recirculating a selected separated fraction oi the treated fluid from the, reaction chamber .to each of a plurality of locations in the treating path, and cont-i ously regulating the'percentag'e recirculated in accordance with a continuous determination of density of the fluid subsequentto the initiation of treatment.

14. The method of processing petroleum'hydrocarbon, which, includes, flowing thefluid un-'- der pressure through a confined path comprising 00, i away, supplying liquid to the system in excess over the vapor rate of discharge, and maintaining the excess constant responsive to density'ot the'liquid-vapor mixture.

' 9. The method of operating a fluid treating system wherein a portion of the entering fluid is vaporized, which includes, passing the llquidand vapor mixture to a relatlvelyquiescent separator section, allowingthe vapors to separate and pass away, supplying liquid to the system in excess over thevapor rate of discharge, and maintaining the percentage excess constant responsive to density of the liquid-vapor mixture.-

10. The method of processing a D IQleum hydrocarbon, which includes, flowlng'the fluid una preheating and a conversion section having a'plurality of parallel paths, separately heating the sections of the path, passing the liquidvapor-gas mixture from the conversion section to a reaction chamber constituting a relatively quiescent separator zone to effect a separation of the 1iquid,"recirculating a portion of the treated fluid to theentrance of the conversion 4 Section, continuously regulating the recirculation rate in accordance with a continuous determine-v tion or density of the fluid leaving the conversion section, and utllizlng'the pressure drop of a p0rtion r each of the plurality r parallel paths 0:3

the conversion zone to introduce the recirculated fluldto the paths and toproperly proportion its j distribution. l

15. The method of processing petroleum hydrocarbon, which includes, fiowing the fluid under pressure through a confined path'coniprising a preheating and a conversion section, separately heating the sections of the path, passing the liquid-vapor-gas mixture from the conversion section to a reaction chamber constituting a relatively quiescent separator zone to effect a sepafor treating the fluid, means determining density.

of the fluid entering said zone, and means under the control of said means for recirculating fluid from adjacent said zone to a selected location in 4 the flow path. l

17. In a petroleum hydrocarbon treating system, in combination, a heated forced circulation path for a selected fluid undergoing treatment, a

reaction chamber to which the fluid in the path discharges as a liquid-vapor mixture, measuring means continuously determining density ofthe' liquid-vapor mixture of fluid entering the reaction chamber, and means for recirculating vapors I and gas. from the reaction chamber to the treating path at a location subsequent to the initiation of treatment, said last named means controlled by said measuring means.

. 18. In a petroleum'hy ocarbon treating sys tem,-in combination, a heated forced circulation path for a selected fluid undergoing treatment,

a-reaction chamber to which the fluid in the path,

discharges as a liquid vapor mixture, measuring means continuously determining density of the liquid-vapor mixture of fluid entering the reaction chamber, and means for recirculating liquid from the reaction chamber to the' treating path at a location subsequent to the initiation of treat I ment, said last named means controlled by said measuring means.- 4 1 e 19. Incombination, a forced circulation fluid treating system including, a flow path to which a selected fluidis supplied under pressure, a separating zone to which the path discharges, heating means for the path, means determining density of the treated liquid-vapor mixture of fluid entering the separator, means for recirculating a sity determining means adapted to regulate the recirculationr 2'0, The method of operating a vapor generator of the forced flow type, which includes, passing the fluid successively through a preheating sec-v tion and a generating section of the path and into-a liquid-vapor separator, heating. the path,

' and recirculating fluid from the separator to a selected location in the flow path in accordance with a determination or density otthe liquidvapor mixture of thefluid entering the separator.

21'. In combination with a'torced flow vapor generator having a preheating and-a generating" section of the path to which a selected fluid is supplied and connected in series, a'separator to which the patndischarges, heatingmeans tor the l path, means recirculating fluid the sepameans determining density of the liquid-vapor mixture or the fluidentering the-separator adaptedwto control the recirculating means.- 1

22. The method of operating a. vapor generator 5 of the forcedflow type having a separator between the generating and superheatlnz P rtions of the flow path, which includes, passing fluid under pressure through a plurality of parallelci're cults in the generating portion, recirculating a material percentage of the liquid entering the generating circuits through saidcircuits, and utilizing flow responsive elements in. connection with the indivi ual circuits to proportion the recirculation to t e circuits.

'23; The methdd of operating a vapor generator of the forced flow type having a separator be: tween the generating and superheating portions a of the flow path, which includes, passing fluid under pressure through a plurality-oi parallel circuits in the generating portion, recirculating a material percentage of the liquid entering the generating circuits through said circuits, separately measuring the weight rate of flow of fluid through the parallel circuits, comparing such. measurements, and using the comparison to proportion recirculated fluid to the parallel circuits.

24. The method of operating a forced circulation fluid treating system comprising a plurality of parallel flow circuits, which includes, supplying o fluid under pressure to the-entrance of the circults, heating the circuits, passing the treated fluid to a relatively quiescent separator zone, passing the gas and vapor away and measuring its weight rate of flowfrecirculating a portion of the separated liquidto the entrance of the processin! zone, separately obtaining a flow indication for 25. In combination, a vapor generator oi the .forced flow type having a plurality of tube circults in the g'eneratingportion-of the path. l relatively quiescent separator zone following thegenerating portion, means returning liquid from the separator and introducing it at the, entrance of each of the tube clrcuits,; means-responsive to load on the unit, means responsive to 'flow'in the individual circuits, and regulating means Jointly positioned by said last 'two named means and adapted to proportion the returned liquid to the several circuits.

26. In combination, a vapor generator of the forced flow type having a plurality of circuits in the generating portion of the path, a

portion of treated fluid to a selected location in relatively m 881mm? 10110!!! ,the flow path, and means controlled by the den generating portion, means returning liquid item the separator and introducing it near the entrance and separatelyto each 01' the tube'circults, a rate, of flow meter or the-vapors leaving the '60 separator, and a pump for iorcing the returned liquid into the circuits: mder the control of said flow meter.

27. In combination, a-vapor generator of the forced flow typehaving a plurality 0!. tube circ5 cults in the generating portion 01' th'giipath, a

liquid-vapor separator to which thejclrcuits discharge, means retuming' liquid under pressure from the'separator to the "entrance 0'! thecircuits, apressure' din'erentinl responsive device for a each. circuit-sensitive w the total fluid nev through the related circuit, and a branch conduit 1 having a regulating valve therein branching the return liquid to each of the circuits, each regal!- lng valve under the. control or its related prev '7 5 sure difl'ercntial responsivedeviee, p

1 I 2,324,513 28. In. combination, a fluid treating system of the type having a plurality of parallel forced circulation tube circuits, a separator to which the tubes discharge, heating means for the circuits, means determining rate of vapor and gas flow from the separator, a pump returning liquid from the separator to the entrancetof the circuits,

means sensitive to a'flowrate variable for eachwot thecircuits, and means responsive to the flow rate means and to the variable sensitive means continuously proportioning theretumed liquid to thefcircuits.

- 'RArMoND n. 'JUNKINS. I 

